This globe shows the ages of rocks that make up the seafloor of the Atlantic Ocean basin. The oceanic crustal rocks are youngest (red) near the Mid-Atlantic Ridge. The seafloor basalts are progressively older (yellow, green) further from the spreading ridge. Plate tectonics gradually moves new basalts, which form as lava hardens at the spreading ridge, away from the ridge. The oldest rocks in the Atlantic (blue), along the coasts of North America and Northern Africa, are about 180 million years old. Image courtesy of NOAA.